Volute for centrifugal pump

ABSTRACT

A casing  10  of a pump has first and second casing elements  20, 30.  Each of the casing elements has a mating face and these mating faces are sealingly joined. An interior of the first casing element defines a portion of a chamber  50  in which the impeller is mounted. A first interior portion of the second casing element defines the remaining portion of the impeller chamber, and a second interior portion defines a diffusion chamber  60  that is in fluid communication with the impeller chamber. Fluid entering the casing at a fluid inlet  34  passes into the impeller chamber, where velocity is imparted to the fluid. The velocity-enhanced fluid passes axially into the diffusion chamber, which has an expanding cross-sectional area along its length, to convert the velocity into pressure head, which is achieved increasing by at least one of: the radially-inward width and the axial height.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of, and makes claim of the benefit of priority to, U.S. provisional patent application Ser. No. 61/082,711, filed 22 Jul. 2008, which is incorporated by reference as if fully recited herein.

TECHNICAL FIELD

The disclosed embodiments of the present invention relate to an improved design for a diffusion chamber for a centrifugal pump, as well as a centrifugal pump comprising such a diffusion chamber, especially one in which the diffusion chamber is in the nature of a volute. In the disclosed embodiments, the expanding cross-sectional area of the diffusion chamber along a length thereof is achieved by an increase of at least one of: the inwardly-extending width of the chamber in the radial direction and the height of the chamber, in the axial direction. There are a variety of applications for such pumps, particularly in commercial appliances.

BACKGROUND OF THE ART

The concept of a centrifugal pump is known in the art. Stated very generally, a centrifugal pump with a volute chamber has an impeller, which is typically vaned. When a drive source, typically an electrical motor, rotates the impeller, the pressure decrease from the rotation causes liquid to be sucked into a chamber in which the impeller is arranged, along a suction line that is typically co-axial with the drive source. The impeller rotation throws the liquid outwardly in a tangential manner, the liquid gaining velocity as it is moved outwardly by the impeller. Positioned radially beyond the impeller, the volute chamber has a smoothly increasing volume, terminating at a tangential discharge. As liquid moves around this volute, the velocity head of the liquid is converted to pressure head. Operation of a centrifugal pump is commonly plotted on a graph of total pressure head as a function of pump volumetric flow rate, or impeller speed, which is directly related to pump volumetric flow rate. A particular pump will always operate along this characteristic curve.

In the known art, the volute chamber has a generally constant height in the axial direction and is generally positioned symmetrically to a radial extension of a line defined by a midpoint of the impeller's thickness. To provide the increasing cross-sectional area, the radial extent of the volute chamber increases from the inlet of the volute chamber to the outlet, imparting a spiral shape to the volute chamber, when viewed axially. Indeed, the very term “volute” is derived from the Latin term for “scroll.”

In many applications, but especially with applications for pumping liquids, as in commercial appliances such as washing machines, it is desirable to provide a compact “footprint” to the pump, and especially the pump casing, in the radial direction. It is also desirable to provide a pump casing that is circular in the radial direction. It is also desirable to provide a pump casing in which the ratio of the impeller diameter to the outside pump casing diameter is as large as possible, since pump performance, both in terms of volume of liquid delivered and feet of total head, increases with impeller diameter.

SUMMARY OF THE INVENTION

This and other unmet objectives of the prior art are met by a casing for housing an impeller. The casing comprises a first casing element, a second casing element and means for sealingly mating faces of the casing elements intended for that purpose. An interior of the first casing element defines a portion of a chamber for the impeller, the impeller chamber portion being located proximate to the mating face. The second casing element has first and second interior portions. The first interior portion defines the remaining portion of the impeller chamber and is proximate to the mating face of the second casing element. The second interior portion defines a diffusion chamber in fluid communication with the impeller chamber.

In some embodiments, the casing also comprises an opening in the first casing element, co-axial with the impeller chamber, for connecting the impeller in the impeller chamber to a drive source external to the casing.

In some embodiments, a suction inlet in the second casing element, co-axial with the impeller chamber, communicates the impeller chamber with the exterior of the casing.

In some embodiments, the second casing element further comprises a radially-extending disk that separates the impeller chamber from the volute chamber. In some of these embodiments, the radially-extending disk has a diameter that is at least as large as a diameter of a base plate of the impeller. In these embodiments, a gap between a circumference of the radially-extending disk and an interior wall of the second casing element provides the fluid communication between the impeller chamber and the diffusion chamber. When the radially-extending disk and the interior wall are co-axial and circular, the gap is annular.

In some embodiments, the second casing element interior wall is located at a constant radial distance from an axis of the impeller.

In many of the embodiments, the second casing element has a tangential outlet that communicates the diffusion chamber with the casing exterior.

In the embodiments, the cross-sectional flow area of the diffusion chamber increases from a first end thereof to a second end, where the tangential outlet is located, the increase being smooth and monotonic.

In these embodiments, a fluid conduit through the casing is defined by, in this order, the suction inlet, the impeller chamber, the volute chamber and the tangential outlet.

In some embodiments, the sealingly mating means comprises a radially-extending circular flange at a circumferential edge of the mating face of each of the casing elements. Occasionally, a gasket will be interposed between the respective radially-extending circular flanges.

Further aspects of the invention are achieved by a centrifugal pump, comprising an impeller casing as described above and an impeller arranged for rotation in the impeller chamber.

Other aspects of the invention are achieved by a casing for housing an impeller, the impeller having a base plate that defines a radial direction of the casing, with an axial direction of the casing normal to the radial direction. The casing comprises a body in which the impeller is housed and a fluid conduit formed within the body. The fluid conduit comprises a fluid inlet, an impeller chamber, in which rotation of the impeller imparted velocity to fluid entering through the fluid inlet, a diffusion chamber for volumetrically expanding fluid received from a fluid communication with the impeller chamber along a length of the diffusion chamber, the diffusion chamber characterized by a cross-sectional area that increases from a first end to a second end thereof, the increase in cross-sectional area provided by expansion of the diffusion chamber in at least one of the radially inward direction and the axial direction; and a fluid outlet, communicating the second end of the diffusion chamber with an exterior of the body.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the disclosed embodiments will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which:

FIG. 1 is a side sectional view of an embodiment of the fluid-handling portion of the centrifugal pump; and

FIG. 2 is an end elevation view of the FIG. 1 embodiment, taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows a side sectional view of an embodiment 10 of a fluid-handling casing of a centrifugal pump. The casing 10 is depicted as a body formed in two pieces, namely a first and a second casing element 20, 30. The exact number of casing elements used to comprise the body may vary, as long as the impeller, described in more detail below, is disposed therein. The exact structure of the casing elements may also vary. The interior of the casing 10, as will be described, has a primary or impeller chamber 50 and a diffusion chamber 60.

The first casing element 20 is intended for attachment to the pump motor (not shown), typically by way of mounting feet 22, two of which are visible in FIG. 1. These mounting feet 22 will commonly be integrally molded as a part of the first casing element 20. Other mounting means will be known to those of skill in the art. A central opening 24 allows passage of a drive shaft (not shown) that transmits drive torque from the motor to an impeller 70 that is rotatingly situated in the impeller chamber 50. The impeller 70 depicted will generally be known to one of skill in the art. The depicted embodiment of the impeller 70 comprises a base plate 72, having a first face 74 with means for radially expelling fluids, particularly liquids, disposed thereon and a second face 76, typically provided with means for mounting to the drive shaft thereon. The radially-expelling means will typically be vanes 78. The impeller may be of many different designs well known to those skilled in the art. The axial height of the primary chamber 50 must be large enough to provide clearance for the impeller 70, but it can be much larger as required for the specific embodiment, as measured from the second face 76 to the distal end of the vanes 78.

The depicted embodiment 10 shows both casing elements 20, 30 provided with radially-extending flanges 26, 36, respectively, by which the casing elements are mated together in a sealing manner. As depicted, each of the casing elements 20, 30 provide about one-half of the total volume that constitutes primary chamber 50, while all of the volume of diffusion chamber 60 is situated in the secondary casing element 30.

While the depicted embodiment shows radially-extending flanges 26, 36 that are circular, it will be known to those of skill in this art to provide variations on the means for sealingly mating the respective casing elements 20, 30. It will also be known to interpose a gasket or similar sealant between the flanges 26, 36 or other mating means.

The second casing element 30 is also provided with a suction inlet 34, through which fluid is drawn into the center of impeller 70. Accordingly, it is preferred to arrange suction inlet 34 so that it is concentric with the impeller 70 and the drive shaft, such that the liquid is directed onto the vanes 78. A separation disk 38 extends radially from the suction inlet 34. The separation disk 38, which has a diameter that is preferred to be at least as large as the diameter of impeller base plate 72, operates with a radially-extending interior wall of the first casing element 20 to define the primary or impeller chamber 50, which is essentially cylindrical.

At the radially outward edge of separation disk 38, a space 80, which is in this case an annular space, is formed between the disk and an interior axial wall 40 of the second casing element. The annular space 80 communicates the impeller chamber 50 to the diffusion chamber 60, and has a width of one to two times the distance from the first face 74 to the distal end of the vanes 78.

Reference is now made to FIG. 2, which shows the fluid handling casing 10 as seen down the axis thereof, that is, along line 2-2 of FIG. 1. A portion of three mounting feet 22 are visible behind second casing element 30, where flange 36 is also visible, with a plurality of bolt holes 42 are shown as the manner for sealing the respective casing elements. The cylindrical nature of the flange 36 and its concentricity with suction inlet 34 are readily noted. A tangential outlet 44 of the second casing element 30, which was not visible in FIG. 1, is seen in FIG. 2. In combination with the suction inlet 34, the impeller chamber 50 and the diffusion chamber 60, this tangential outlet 44 defines the fluid conduit through the casing 10.

Referring now to both FIGS. 1 and 2, the shape of the diffusion chamber 60 will be understood. Moving counterclockwise from the tangential outlet 44, that is, in the reverse direction of the intended fluid flow, the diffusion chamber 60 smoothly and monotonically decreases in cross-sectional flow area, as is readily observed in FIG. 2. This decrease is achieved, at least in the depicted embodiment, by decreasing both the width of the diffusion chamber 60 in the radially-inward direction and the height in the axial direction, while maintaining a constant outside diameter. In some instances, this decrease of area may be achieved by decreasing only one of these dimensions.

Viewing the disclosed embodiment of FIGS. 1 and 2 in a different manner, a casing 10 is provided for housing an impeller 70. The impeller 70 has a base plate 72 and this base plate defines a radial direction of the casing, with an axial direction of the casing being normal to the radial direction. The casing has a body 10 in which the impeller 70 is housed. The body 10 has a fluid path formed within it. This fluid path commences at a fluid inlet 34, which admits fluid into the body interior, particularly to an impeller chamber 50, where rotation of the impeller 70 imparts energy in the form of velocity to the fluid. A diffusion chamber 60 is provided, in fluid communication with the impeller chamber 50 along a length of the diffusion chamber, so that the fluid thrown radially outward by the impeller passes into the diffusion chamber. In the embodiment shown, the fluid communication between the impeller chamber 50 and the diffusion chamber 60, which is axially displaced from the impeller chamber in the disclosed embodiment, is provided by annular gap 80. In the diffusion chamber 60, the energy represented by the increased velocity is converted into pressure or head, by cross-sectional area that increases from a first end to a second end. This increase in cross-sectional area is provided by increasing at least one of: the radially-inward width of the diffusion chamber and the height of the diffusion chamber in the axial direction, especially in the direction away from the impeller 70. At the second end of the diffusion chamber 60, the fluid path terminates at a fluid outlet 44, which is open to the exterior of the body 10.

Industrial applicability of the device described herein is found in a number of devices. One example is a pump housed in an industrial/commercial dishwasher and used for pressurizing the hot cleaning water.

Having shown and described a preferred embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Thus, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention. It is not the intention, therefore, to limit the invention only as indicated by the scope of the claims. 

1. A casing for housing an impeller, comprising: a first casing element, an interior thereof defining a portion of a chamber for the impeller, the impeller chamber portion proximate to a mating face of the first casing element; and a second casing element, a first interior portion thereof defining the remaining portion of the impeller chamber, the remaining portion of the impeller chamber proximate to a mating face of the second casing element, and a second interior portion of the second casing element defining a diffusion chamber in fluid communication with the impeller chamber; and means for sealingly mating the respective mating faces.
 2. The casing of claim 1, further comprising: an opening in the first casing element, co-axial with the impeller chamber, for connecting the impeller in the impeller chamber to a drive source external to the casing.
 3. The casing of claim 2, further comprising: a suction inlet in the second casing element, co-axial with the impeller chamber and communicating the impeller chamber with the exterior of the casing.
 4. The casing of claim 1, further comprising: a radially-extending disk in the second casing element, which separates the impeller chamber from the diffusion chamber.
 5. The casing of claim 4, wherein: the radially-extending disk has a diameter that is at least as large as a diameter of a base plate of the impeller.
 6. The casing of claim 5, further comprising: a gap between a circumference of the radially-extending disk and an interior wall of the second casing element that provides the fluid communication between the impeller chamber and the diffusion chamber.
 7. The casing of claim 6, wherein: the gap is annular.
 8. The casing of claim 6, wherein: the second casing element interior wall is located at a constant radial distance from an axis of the impeller.
 9. The casing of claim 3, further comprising: a tangential outlet in the second casing element, communicating the diffusion chamber with the exterior of the casing.
 10. The casing of claim 9, wherein: a cross-sectional flow area of the diffusion chamber decreases smoothly and monotonically in an angular direction away from the tangential outlet.
 11. The casing of claim 9, wherein: a fluid conduit through the casing is defined by the suction inlet, the impeller chamber, the diffusion chamber and the tangential outlet.
 12. The casing of claim 1, wherein: the sealingly mating means comprises a radially-extending circular flange at a circumferential edge of the mating face of each of the casing elements.
 13. The casing of claim 12, further comprising: a gasket interposed between the respective radially-extending circular flanges.
 14. A centrifugal pump, comprising: an impeller casing according to claim 1; and an impeller arranged for rotation in the impeller chamber.
 15. A casing for housing an impeller, the impeller having a base plate that defines a radial direction of the casing, with an axial direction of the casing normal to the radial direction, the casing comprising: a body in which the impeller is housed; and a fluid conduit formed within the body, the fluid conduit comprising: a fluid inlet; an impeller chamber, in which rotation of the impeller imparted velocity to fluid entering through the fluid inlet; a diffusion chamber for volumetrically expanding fluid received from a fluid communication with the impeller chamber along a length of the diffusion chamber, the diffusion chamber characterized by a cross-sectional area that increases from a first end to a second end thereof, the increase in cross-sectional area provided by expansion of the diffusion chamber in at least one: of the radially inward direction and the axial direction; and a fluid outlet, communicating the second end of the diffusion chamber with an exterior of the body. 